Storage system with modular container handling vehicles

ABSTRACT

A storage system including a storage grid including vertical column profiles defining a plurality of grid columns. The grid columns include storage columns, in which storage containers can be stored one on top of another in vertical stacks. The storage grid including at least one rail grid at the upper ends of the column profiles, and a first container handling vehicle and a second container handling vehicle. The first and the second container handling vehicles each include at least one wheel base unit and a first container handling module or a second container handling module. Each wheel base unit having a wheel arrangement for movement of the wheel base unit in two perpendicular directions upon a rail grid of the storage system. The first container handling module is a different type of container handling module to the second container handling module.

TECHNICAL FIELD

The present invention relates to the field automated storage systems.

BACKGROUND

FIGS. 1A and 2B disclose a typical prior art automated storage andretrieval system 1 with a framework structure 100. FIGS. 1B and 2Bdisclose prior art container handling vehicles 200,300 operating in thesystem 1 disclosed in FIGS. 1A and 2A, respectively.

The framework structure 100 defines a storage grid 104 comprising aplurality of upright members 102 and optionally a plurality ofhorizontal members 103 supporting the upright members 102. The members102, 103 may typically be made of metal, e.g., extruded aluminumprofiles.

The storage grid 104 comprises multiple grid columns 112. A largemajority of the grid columns are also termed storage columns 105, inwhich storage containers 106, also known as bins, are stacked one on topof another to form stacks 107.

Each storage container 106 may typically hold a plurality of productitems (not shown), and the product items within a storage container 106may be identical or may be of different product types depending on theapplication.

The grid columns 112 of the storage grid 104 guard against horizontalmovement of the of storage containers 106 in the stacks 107, and guidesvertical movement of the containers 106, but does normally not otherwisesupport the storage containers 106 when stacked.

The automated storage and retrieval system 1 comprises a rail system 108(or a top rail grid) arranged in a grid pattern across the top of thestorage grid 104, on which rail system 108 a plurality of containerhandling vehicles 200,300 (as exemplified in FIGS. 1B and 2B) areoperated to raise storage containers 106 from, and lower storagecontainers 106 into, the storage columns 105, and also to transport thestorage containers 106 above the storage columns 105. The horizontalextent of one of the grid cells 122 constituting the grid pattern is inFIGS. 1A and 2A marked by thick lines.

Each grid cell 122 has a width which is typically within the interval of30 to 150 cm, and a length which is typically within the interval of 50to 200 cm. Each grid opening 115 has a width and a length which istypically 2 to 10 cm less than the width and the length of the grid cell122 due to the horizontal extent of the rails 110,111.

The rail system 108 comprises a first set of parallel rails 110 arrangedto guide movement of the container handling vehicles 200,300 in a firstdirection X across the top of the frame structure 100, and a second setof parallel rails 111 arranged perpendicular to the first set of rails110 to guide movement of the container handling vehicles 200,300 in asecond direction Y which is perpendicular to the first direction X. Inthis way, the rail system 108 defines the upper ends of the grid columns112 above which the container handling vehicles 200,300 can movelaterally, i.e., in a plane which is parallel to the horizontal X-Yplane. Commonly, at least one of the sets of rails 110,111 is made up ofdual-track rails allowing two container handling vehicles to pass eachother on neighboring grid cells 122. Dual-track rails are well-known anddisclosed in for instance WO 2015/193278 A1 and WO 2015/140216 A1, thecontents of which are incorporated herein by reference. Each prior artcontainer handling vehicle 200,300 comprises a vehicle body and a wheelarrangement of eight wheels 201,301, wherein a first set of four wheels32 a enable the lateral movement of the container handling vehicles200,300 in the X direction and a second set of four wheels 32 b enablethe lateral movement in the Y direction. One or both sets of wheels inthe wheel arrangement can be lifted and lowered, so that the first setof wheels and/or the second set of wheels can be engaged with therespective set of rails 110, 111 at any one time.

Each prior art container handling vehicle 200,300 also comprises alifting device 18 (only shown in FIG. 2B) for vertical transportation ofstorage containers 106, e.g., raising a storage container 106 from, andlowering a storage container 106 into, a grid column 112. The liftingdevice 18 comprises four metal lifting bands 16 extending in a verticaldirection and connected close to the corners of a lifting frame 17 (mayalso be termed a gripping device) such that the lifting frame is kepthorizontal. The lifting frame 17 features container connecting elements24 for releasable connection to a storage container, and guiding pins30.

Conventionally, and also for the purpose of this application, Z=1identifies the uppermost layer of the storage grid 104, i.e., the layerimmediately below the rail system 108, Z=2 the second layer below therail system 108, Z=3 the third layer etc. In the prior art storage griddisclosed in FIGS. 1A and 2A, Z=8 identifies the lowermost, bottom layerof the storage grid 104. Consequently, as an example, and using theCartesian coordinate system X, Y, Z indicated in FIGS. 1A and 2B, thestorage container identified as 106′ in FIG. 1 can be said to occupygrid location or cell X=10, Y=2, Z=3. The container handling vehicles200,300 can be said to travel in layer Z=0 and each grid column can beidentified by its X and Y coordinates. Each container handling vehicle200 comprises a storage compartment or space (not shown) for receivingand stowing a storage container 106 when transporting the storagecontainer 106 across the top of the storage grid 104. The storage spacemay comprise a cavity arranged centrally within the vehicle body, e.g.,as is described in W02014/090684A1, the contents of which areincorporated herein by reference. Alternatively, the container handlingvehicles 300 may have a cantilever construction as described inN0317366, the contents of which are also incorporated herein byreference.

The container handling vehicles 200 may have a footprint, i.e., anextent in the X and Y directions, which is generally equal to thehorizontal area of a grid cell 122, i.e., the extent of a grid cell 122in the X and Y directions, e.g., as is described in WO2015/193278A1, thecontents of which are incorporated herein by reference. Alternatively,the container handling vehicles 200 may have a footprint which is largerthan the horizontal area of a grid cell 122, e.g., as is disclosed inW02014/090684A1.

In a storage grid 104, most of the grid columns 112 are storage columns105, i.e., grid columns wherein storage containers 106 are stored instacks 107. However, a storage grid 104 normally has at least one gridcolumn 112 which is not used for storing storage containers 106, but isarranged at a location wherein the container handling vehicles 200,300can drop off and/or pick up storage containers 106 so that they can betransported to a second location (not shown) where the storagecontainers 106 can be accessed from outside of the storage grid 104 ortransferred out of or into the grid 104. Within the art, such a locationis normally referred to as a “port” and the grid column 112 at which theport is located may be referred to as a transfer column 119,120. Thedrop-off and pick-up ports are the upper ends/openings of a respectivetransfer column 119,120.

The prior art storage grids 104 in FIGS. 1A and 2A comprise two transfercolumns 119 and 120. The first transfer column 119 may for examplecomprise a dedicated drop-off port where the container handling vehicles200,300 can drop off storage containers 106 to be transported throughthe transfer column 119 and further to e.g., a picking/stocking station,and the second transfer column 120 may comprise a dedicated pick-up portwhere the container handling vehicles 200,300 can pick up storagecontainers 106 that have been transported through the transfer column120 from e.g., a picking/stocking station. A storage container may betransported through a transfer column by use of the lifting device of acontainer handling vehicle 200,300 or by use of a storage container liftarranged in the transfer column. Each of the ports of the first andsecond transfer column may be suitable for both pick-up and drop-off ofstorage containers.

The second location may typically be a picking/stocking station, whereinproduct items are removed from and/or positioned into the storagecontainers 106. In a picking/stocking station, the storage containers106 are normally never removed from the automated storage and retrievalsystem 1 but are returned into the storage grid 104 once accessed.

For monitoring and controlling the automated storage and retrievalsystem 1, e.g., monitoring and controlling the location of respectivestorage containers 106 within the storage grid 104; the content of eachstorage container 106; and the movement of the container handlingvehicles 200,300 so that a desired storage container 106 can bedelivered to the desired location at the desired time without thecontainer handling vehicles 200,300 colliding with each other, theautomated storage and retrieval system 1 comprises a computerizedcontrol system (not shown) which typically comprises a database forkeeping track of the storage containers 106.

A conveyor system including conveyor belts or rollers is commonlyemployed to transport the storage containers from a lower end of thetransfer columns 119,120 to e.g., a picking/stocking station.

A conveyor system may also be arranged to transfer storage containersbetween different storage grids, e.g., as is described inWO2014/075937A1, the contents of which are incorporated herein byreference.

Further, WO2016/198467A1, the contents of which are incorporated hereinby reference, discloses an example of a prior art access system havingconveyor belts (FIGS. 5a and 5b in WO2016/198467A1) and a frame mountedrail (FIGS. 6a and 6b in WO2016/198467A1) for transporting storagecontainers between transfer columns and stations where operators canaccess the storage containers.

When a storage container 106 stored in the storage grid 104 disclosed inFIG. 1A is to be accessed, one of the container handling vehicles200,300 is instructed to retrieve the target storage container 106 fromits position in the storage grid 104 and transport it to or through thetransfer column 119. This operation involves moving the containerhandling vehicle 200,300 to a grid location above the storage column 105in which the target storage container 106 is positioned, retrieving thestorage container 106 from the storage column 105 using the containerhandling vehicle's lifting device (not shown), and transporting thestorage container 106 to the transfer column 119. If the target storagecontainer 106 is located deep within a stack 107, i.e., with one or aplurality of other storage containers positioned above the targetstorage container 106, the operation also involves temporarily movingthe above-positioned storage containers prior to lifting the targetstorage container 106 from the storage column 105. This step, which issometimes referred to as “digging” within the art, may be performed withthe same container handling vehicle 200,300 that is subsequently usedfor transporting the target storage container 106 to the transfercolumn, or with one or a plurality of other cooperating containerhandling vehicles 200,300. Alternatively, or in addition, the automatedstorage and retrieval system 1 may have container handling vehicles200,300 specifically dedicated to the task of temporarily removingstorage containers 106 from a storage column 105. Once the targetstorage container 106 has been removed from the storage column 105, thetemporarily removed storage containers can be repositioned into theoriginal storage column 105. However, the removed storage containers mayalternatively be relocated to other storage columns 105.

When a storage container 106 is to be stored in the grid 104, one of thecontainer handling vehicles 200,300 is instructed to pick up the storagecontainer 106 from the transfer column 120 and to transport it to a gridlocation above the storage column 105 where it is to be stored. Afterany storage containers positioned at or above the target position withinthe storage column stack 107 have been removed, the container handlingvehicle 200,300 positions the storage container 106 at the desiredposition. The removed storage containers may then be lowered back intothe storage column 105 or relocated to other storage columns 105.

The applicant is developing highly advantageous solutions for obtainingstorage systems that are both more efficient and flexible than the priorart systems. A common feature of these solutions is the requirement ofmultiple types of storage system vehicles for moving upon a rail grid,wherein each type of vehicle is specifically designed to be effectivewhen performing a dedicated operation, such as transport of storagecontainer, lifting of storage containers, digging etc. An optimumperformance of the different storage system vehicles may be obtainedwhen the vehicles are designed independent of each other. However,having different types of storage system vehicles designed independentlyof each other may have some disadvantages related to costs in that theymay require different spare parts, require different solutions forcharging of the vehicle batteries, different constructions of the wheelarrangement allowing them to move upon a rail grid etc.

The aim of the present invention is to alleviate or mitigate at leastsome of the possible disadvantages related to the construction ofmultiple types of vehicles for moving upon a rail grid of a storagesystem.

SUMMARY

The present invention is defined by the appended claims and in thefollowing. In a first aspect, the present invention provides a storagesystem including: a storage grid including vertical column profilesdefining a plurality of grid columns, the grid columns comprise storagecolumns, in which storage containers can be stored one on top of anotherin vertical stacks, the storage grid including at least one rail grid atthe upper ends of the column profiles; a first container handlingvehicle and a second container handling vehicle, the first and thesecond container handling vehicles each including at least one wheelbase unit and a first container handling module or a second containerhandling module, respectively, connected to the wheel base unit; eachwheel base unit having a wheel arrangement for movement of the wheelbase unit in two perpendicular directions upon a rail grid of thestorage system and a horizontal periphery fitting within the horizontalarea defined by a grid cell of the rail grid such that two wheel baseunits may pass each other on any adjacent grid cells of the rail grid,each of the wheel base units comprises an upper surface configured as aconnecting interface for connection to any of the first and secondcontainer handling modules, and the first container handling module is adifferent type of container handling module to the second containerhandling module.

In other words, the first type of container handling vehicle features acontainer handling module different to the container handling module ofthe second type of container handling vehicle.

In other words, the second type of container handling vehicle mayfeature any of the container handling modules not comprised by the firsttype of container handling vehicle.

In an embodiment of the storage system, the grid columns comprisestorage columns, in which storage containers can be stored one on top ofanother in vertical stacks, and at least one transfer column, each ofthe grid columns being defined by four vertically extending columnprofiles, and the column profiles are

interconnected at their upper ends by top rails forming a horizontal toprail grid of the storage grid.

In an embodiment of the storage system, the first and/or the secondcontainer handling vehicles can lift and lower a storage containerwithin a grid column and/or transfer a storage container upon a railgrid.

Each of the first and the second container handling module may comprisea connecting interface for connection to at least one wheel base unit,the connecting interface may be arranged to connect to the upper surfaceof a wheel base unit.

In an embodiment of the storage system, the connecting interface of thewheel base unit comprises a horizontal top panel featuring multipleconnecting elements. The top panel may comprise a center opening, i.e.,such that the top panel forms a flange extending inwards from theperiphery of the wheel base unit.

The connecting elements of the top panel/flange may be through-holes orbolts arranged to interact with corresponding bolts or through-holes ofthe connecting interface of the container handling modules. In anembodiment, the connecting interface of both the wheel base unit and thecontainer handling modules comprises corresponding through-holes and thewheel base unit is connected to a container handling module by bolts.

In an embodiment of the storage system, each of the first and the secondcontainer handling module comprises a connecting interface forconnection to the connecting interface of the wheel base unit.

In an embodiment of the storage system, the connecting interface of thefirst and the second container handling module comprises connectingelements arranged at positions corresponding to the multiple connectingelements of the top panel/flange.

In an embodiment of the storage system, the top panel/flange features acenter opening allowing access to internal components of the wheel baseunit. The internal components may include electric motors for drivingthe wheel arrangement, a rechargeable battery and electronic controlsystems. Access to the rechargeable battery and the electronic controlsystem allows them to be easily connected to a container handling moduleconnected to the wheel base unit.

In an embodiment of the storage system, one of the first and the secondcontainer handling modules includes a cantilever section having alifting device, wherein the container handling module is connected to asingle wheel base unit and the lifting device is arranged to raise andlower a storage container within a grid column positioned below thecantilever section.

In an embodiment of the storage system, one of the first and the secondcontainer handling modules includes a bridge section to which at leastone lifting device is connected, wherein the container handling moduleis connected to two separate wheel base units, such that the bridgesection is supported by a wheel base unit at each of two opposite endsand the lifting device is arranged to raise and lower a storagecontainer within a grid column positioned below the bridge section.

In an embodiment of the storage system, one of the first and the secondcontainer handling modules includes a storage container carrier, whereinthe container handling module is connected to a single wheel base unit,such that a storage container may be supported on top of the wheel baseunit.

In an embodiment of the storage system, one of the first and the secondcontainer handling modules includes a storage container carrier, whereinthe container handling module is connected to a single wheel base unit,the storage container carrier including a conveyor unit, such that astorage container may be supported on top of the wheel base unit andmoved in a lateral direction when the conveyor unit is activated.

In an embodiment of the storage system, the first or the secondcontainer handling vehicle includes two wheel base units and only one ofthe wheel base units includes electric motors for driving the wheelarrangement.

In an embodiment of the storage system, the first container handlingvehicle includes a lifting device arranged to raise and lower a storagecontainer within a grid column.

In an embodiment of the storage system, the first container handlingvehicle includes a cantilever section and a lifting device, the liftingdevice is arranged to raise and lower a storage container within a gridcolumn positioned below the cantilever section and comprises a liftingshaft, a motor for rotating the lifting shaft, a lifting frame forreleasably connecting a storage container, and lifting bands connectingthe lifting shaft to the lifting frame.

The cantilever section may extend beyond a horizontal periphery of thewheel base unit. The cantilever section may extend over a grid cellbeing adjacent to the grid cell occupied by the wheel base unit. Thelifting frame may be suspended from the cantilever section.

In an embodiment of the storage system, the second container handlingvehicle includes a container carrier connected to a single wheel baseunit, such that a storage container may be supported on top of the wheelbase unit.

In an embodiment, the storage system includes a transfer rail grid beingseparate from the rail grid at the upper ends of the column profiles,where the transfer rail grid includes rails upon which the wheel baseunit may move in two perpendicular horizontal directions.

In an embodiment of the storage system, the transfer rail grid isarranged at a level below the level of the rail grid at the upper endsof the column profiles.

In an embodiment of the storage system, the transfer rail grid includesa section arranged below a transfer column of the storage gridstructure, such that the first and/or the second container handlingvehicle may raise or lower a storage container between the rail grid atthe upper ends of the column profiles and a first and/or secondcontainer handling vehicle arranged on the transfer rail grid below thetransfer column.

The horizontal periphery of the wheel base unit may fit within thehorizontal area defined by a grid cell of any of the rail grid at theupper ends of the column profiles and the transfer rail grid.

In a second aspect, the present invention provides a wheel base unit fora storage system according to the first aspect, including a connectinginterface for connection to the first or second container handlingmodule, the connecting interface arranged at a topside of the wheel baseunit and including a top plate having multiple through-holes and acenter opening.

In an embodiment of the wheel base unit, the center opening allowsaccess to at least one of a rechargeable battery and an electroniccontrol system of the wheel base unit.

In an embodiment of the wheel base unit, the wheel arrangement includesa first set of wheels for movement in a first direction upon a rail gridand a second set of wheels for movement in a second directionperpendicular to the first direction, and each set of wheels includestwo pairs of wheels arranged on opposite sides of the wheel base unit.

In a third aspect, the present invention provides a container handlingvehicle for a storage system according to the first aspect, including atleast one wheel base unit and a container handling module having acantilever section including a lifting device, where the containerhandling module is connected to a single wheel base unit.

The lifting device of the container handling vehicle is arranged toraise/lower a storage container and includes a lifting frame forreleasably connecting to a storage container, and optionally liftingbands/wires connecting the lifting frame to a lifting shaft on which thelifting bands/wires may be spooled.

In an embodiment, the container handling vehicle includes a bridgesection to which at least one lifting device is connected and two wheelbase units, the bridge section is connected to one of the wheel baseunits at each of two opposite ends of the bridge section and the liftingdevice is arranged between the wheel base units.

In a fourth aspect, the present invention provides a modular containerhandling vehicle system for a storage system according to the firstaspect, including at least one wheel base unit and at least a first anda second type of container handling module, where the wheel base unitcomprises a wheel arrangement for movement of the wheel base unit in twoperpendicular directions upon a rail grid and an upper surfaceconfigured as a connecting interface for connection to any of the firstand second container handling modules.

In an embodiment of the modular container handling vehicle system, thefirst and the second type of container handling module are selected froma container handling module including: a cantilever section having alifting device, wherein the container handling module is connectable toa single wheel base unit and the lifting device is for raising andlowering a storage container positioned below the cantilever section; abridge section to which at least one lifting device is connected,wherein the bridge section is connectable to two wheel base units, suchthat the bridge section is supported by a wheel base unit at each of twoopposite ends and the lifting device is for raising and lowering astorage container positioned below the bridge section; a storagecontainer carrier connectable to a single wheel base unit, such that astorage container may be supported on top of the wheel base unit; or astorage container carrier connectable to a single wheel base unit, thestorage container carrier including a conveyor unit, such that a storagecontainer may be supported on top of the wheel base unit and moved in alateral direction when the conveyor unit is activated.

In an embodiment of the modular container handling vehicle system, oneof the first and the second type of container handling modules isselected from a container handling module including a cantilever sectionhaving a lifting device, and the lifting device is arranged to raise andlower a storage container positioned below the cantilever section andincludes a lifting shaft, a motor for rotating the lifting shaft, alifting frame for releasably connecting the storage container andlifting bands connecting the lifting shaft to the lifting frame.

BRIEF DESCRIPTION OF DRAWINGS

Certain embodiments of the present invention will now be described indetail by way of example only and with reference to the followingdrawings:

FIGS. 1A and 1B show a perspective side view of a prior art storagesystem and a prior art container handling vehicle.

FIGS. 2A and 2B show a perspective side view of a prior art storagesystem and a prior art container handling vehicle.

FIG. 3 is a perspective side view of a novel storage system.

FIG. 4 is a perspective view of a novel container handling vehicle.

FIG. 5 is a perspective side view of an exemplary embodiment of astorage system according to the invention.

FIGS. 6-11 are perspective views of an exemplary embodiment of a wheelbase unit according to the invention.

FIG. 12 is a perspective view of a modular vehicle system according tothe invention.

FIGS. 13-21 are perspective views of exemplary container handlingvehicles according to the invention. embodiments.

DETAILED DESCRIPTION

The applicant is developing highly advantageous solutions for obtainingstorage systems that are both more efficient and flexible than the priorart systems. A common feature of these solutions is the requirement ofmultiple types of storage system vehicles for moving upon a rail grid,wherein each type of vehicle is specifically designed to be effectivewhen performing a dedicated operation, such as transport of storagecontainer, lifting of storage containers, digging etc. An optimumperformance of the different storage system vehicles may be obtainedwhen the vehicles are designed independent of each other. However,having different types of storage system vehicles designed independentlyof each other may have some disadvantages related to costs in that theymay require different spare parts, require different solutions forcharging of the vehicle batteries, different constructions of the wheelarrangement allowing them to move upon a rail grid.

An embodiment of a storage system being developed by the applicant isdisclosed in FIG. 3 . Similar to the prior art storage systems in FIGS.1 and 2 , the storage grid structure 104 is made up of multiple verticalcolumn profiles 102 upon which a top rail grid 108 is arranged. Thestorage grid structure provides multiple storage columns 105 in whichstorage containers 106 may be stacked on top of each other.

A container handling vehicle 300 is arranged to move in twoperpendicular directions upon the top rail grid 108 and features alifting device to raise and/or lower storage container out of or intothe storage columns, see description in the background section. Inaddition to the features known from the prior art, the storage system inFIG. 3 comprises a transfer rail grid 5 upon which a container transfervehicle may move in two perpendicular directions. The transfer rail grid5 features a section arranged below a transfer column 119,120 such thatthe container handling vehicle may lower a storage container to, orretrieve a storage container from, a container transfer vehicle 400positioned below the transfer column. Further details of the storagesystem in FIG. 3 is described in the Norwegian patent applicationsN020181039 and N020181005, the contents of which is incorporated byreference.

Another container handling vehicle 500 being developed by the applicantis shown in FIG. 4 . The vehicle is somewhat similar to the prior artcontainer handling vehicle 200 in FIG. 1B in that it features a cavity25 in which a storage container 106 may be accommodated. However, inaddition to a lifting device including a lifting frame 17, the vehiclein FIG. 4 comprises a guide shuttle 19 which allows the vehicle to lifta storage container a substantially increased height compared to theprior art vehicles.

Although providing several advantages in obtaining more efficientstorage systems, the requirement of having container vehicles300,400,500 of different designs may also increase the cost of suchstorage systems.

To alleviate some of the costs and potential disadvantages of a storagesystem requiring multiple types container vehicles, the applicant hasdeveloped a new storage system in which the various container vehiclescomprises a common type of wheel base unit. By having a common type ofwheel base unit, many service intensive parts are the same over thewhole range of container vehicles and the production of differentcontainer vehicles are more standardized.

An exemplary embodiment of an inventive storage system is shown in FIG.5 . To better illustrate the present invention, the specific embodimentcomprises five different container vehicles, each featuring the sametype of wheel base unit 2. Each of the different container vehiclesfeatures different container handling modules connected to therespective wheel base unit(s) 2 to obtain the required specializedfunction.

The storage grid structure 104 comprises the same features as thestorage grid structure in FIG. 3 .

An exemplary wheel base unit is shown in FIGS. 6-11 . The wheel baseunit 2 features a wheel arrangement 32 a, 32 b having a first set ofwheels 32 a for movement in a first direction upon a rail grid (i.e.,any of the top rail grid 108 and the transfer rail grid 5) and a secondset of wheels 32 b for movement in a second direction perpendicular tothe first direction. Each set of wheels comprises two pairs of wheelsarranged on opposite sides of the wheel base unit 2. To change thedirection in which the wheel base unit may travel upon the rail grid,one of the sets of wheels 32 b is connected to a wheel displacementassembly 7. The wheel displacement assembly is able to lift and lowerthe connected set of wheels 32 b relative to the other set of wheels 32a such that only the set of wheels travelling in a desired direction isin contact with the rail grid. The wheel displacement assembly 7 isdriven by an electric motor 8. Further, two electric motors 4,4′,powered by a rechargeable battery 6, are connected to the set of wheels32 a, 32 b to move the wheel base unit in the desired direction.

The horizontal periphery of the wheel base unit 2 is dimensioned to fitwithin the horizontal area defined by a grid cell 122, see FIGS. 1-3 ,of the rail grid such that two wheel base units may pass each other onany adjacent grid cells of the rail grid. In other words, the wheel baseunit 2 may have a footprint, i.e., an extent in the X and Y directions,which is generally equal to the horizontal area of a grid cell 122,i.e., the extent of a grid cell 122 in the X and Y directions, e.g., asis described in WO2015/193278A1, the contents of which are incorporatedherein by reference.

The wheel base unit 2 has a top panel/flange 9 (i.e., an upper surface)configured as a connecting interface for connection to a connectinginterface of a selected container handling module. The top panel 9 havea center opening 20 and features multiple through-holes 10 (i.e.,connecting elements) suitable for a bolt 11 connection via correspondingthrough-holes 10′ in the connecting interface of a container handlingmodule, see FIG. 19 for connection between a wheel base unit 2 and acontainer handling module featuring a cantilever section.

In other embodiments, the connecting elements of the top panel 9 may forinstance be threaded pins for interaction with the through-holes 10′ ofthe connecting interface of the container handling module, or viceversa. The presence of a center opening 20 is highly advantageous as itprovides access to internal components of the wheel base unit, such asthe rechargeable battery 6 and an electronic control system 21. Theaccess allows the rechargeable battery 6 and the electronic controlsystem 21 to be easily connected to a container handling moduleconnected to the wheel base unit, thus the container handling module isnot required to have its own dedicated power source and/or controlsystem.

Three different types of container vehicles 300′, 500′, 600′ arearranged on the top rail grid 108. Two different types of containerhandling vehicles 400′,400″ are arranged on the transfer rail grid 5.

The first type of container vehicle 600′ is adapted to lift/lowerseveral storage containers at the same time and is particularly suitedfor digging operations upon the top rail grid. In this embodiment, thecontainer vehicle 600′ comprises four lifting devices having a liftingframe 17, each able to lift a separate storage container. Commonly, thefirst type of container vehicle 600′ will comprise two, three or fourlifting devices. The first type of container vehicle comprises two wheelbase units 2 positioned at opposite ends of the container vehicle 600′.The wheel base units 2 are interconnected by a container handling moduleincluding a bridge section 3 to which the four lifting devices areconnected. When a container vehicle comprises two wheel base units 2,one of the wheel base units 2 may be used without electric motors 4,4′driving the set of wheels 32 a, 32 b. A prior art container vehicleadapted for lifting multiple storage containers and being suitable fordigging operations is disclosed in WO 2019/101366 A1.

The second type of container vehicle 300′ is adapted to perform the samefunctions as the prior art vehicle 300 described above. Details of thesecond type of container vehicle 300′ is shown in FIGS. 16-19 . Thecontainer handling module of the second type of container vehicle 300′comprises a cantilever section 12 featuring a lifting device arranged toraise and lower a storage container within a storage or transfer columnpositioned below the cantilever section (i.e., a container handlingmodule). The lifting device comprises a lifting shaft 22 and a motor 23for rotating the lifting shaft 22, a lifting frame 17 for releasablyconnecting a storage container and lifting bands 16 connecting thelifting shaft to the lifting frame.

The third type of container vehicle 500′ is similar to the containerhandling vehicle 500 shown in FIG. 4 . A detailed view of the third typeof container vehicle 500′ is shown in FIGS. 20 and 21 . The containervehicle 500′ comprises two wheel base units 2 arranged on opposite sidesof a bridge section 3′ (i.e., a container handling module). The bridgesection features a lifting device including a lifting frame 17, a guideshuttle 19, a lifting shaft 22′ upon which wires or lifting bands (notshown) connected to the lifting frame or guide shuttle may be spooled,and a lift motor 23′ for driving the lifting shaft. Further, the bridgesection 3′ features a connecting interface (not shown but comprisesthrough-holes as shown in FIG. 19 ) on each of its opposite sides, eachof the connecting interfaces connected to the connecting interface(i.e., top plate/flange 9) of a corresponding wheel base unit 2. Theguide shuttle is arranged to interact with the vertical column profiles102 of a storage grid structure 104 and prevent detrimental tilting ofthe lifting frame 17, and any storage container 106 connected thereto,when the lifting frame 17 is raised/lowered inside a transfer column119,120.

The fourth 400′ and fifth 400″ type of container vehicle are arranged totravel upon the transfer rail grid 5. Detailed views of the containervehicles 400′, 400″ are shown in FIGS. 13-15 . Both container vehiclescomprise a single wheel base unit 2 and a storage container carrier13,14 (i.e., a container handling module) suitable for supporting astorage container 106. Each of the storage container carriers 13,14comprises a connecting interface suitable for connecting to the topplate/flange 9 (i.e., connecting interface) of the wheel base unit 2.The container handling module 13 of the fourth type of containerhandling vehicle 400′ comprises an open top box-shaped containerreceiver in which a storage container 106 may be accommodated. Thecontainer handling module 14 of the fifth type of container handlingvehicle 400″ comprises a roller conveyor 15 upon which a storagecontainer 106 may be accommodated. By use of the roller conveyor 15, astorage container 106 may be transferred onto or off the containerhandling vehicle 400″ in a lateral direction.

What is claimed is:
 1. A modular container handling vehicle system for astorage system having a horizontal rail grid, the modular containerhandling vehicle system comprising at least one wheel base unit and atleast a first and a second type of container handling module, whereinthe wheel base unit comprises a wheel arrangement for movement of thewheel base unit in two perpendicular directions upon a rail grid and anupper surface configured as a connecting interface for connection to anyof the first and second container handling modules.
 2. A modularcontainer handling vehicle system according to claim 1, wherein thefirst and the second type of container handling module are selected froma container handling module comprising: a cantilever section having alifting device, wherein the container handling module is connectable toa single wheel base unit and the lifting device is for raising andlowering a storage container positioned below the cantilever section; abridge section to which at least one lifting device is connected,wherein the bridge section is connectable to two wheel base units, suchthat the bridge section is supported by a wheel base unit at each of twoopposite ends and the lifting device is for raising and lowering astorage container positioned below the bridge section; a storagecontainer carrier connectable to a single wheel base unit, such that astorage container may be supported on top of the wheel base unit; or astorage container carrier connectable to a single wheel base unit, thestorage container carrier comprising a conveyor unit, such that astorage container may be supported on top of the wheel base unit andmoved in a lateral direction when the conveyor unit is activated.
 3. Amodular container handling vehicle system according to claim 2, whereinone of the first and the second type of container handling modules isselected from a container handling module comprising a cantileversection having a lifting device, and the lifting device is arranged toraise and lower a storage container positioned below the cantileversection and comprises a lifting shaft, a motor for rotating the liftingshaft, a lifting frame for releasably connecting the storage containerand lifting bands connecting the lifting shaft to the lifting frame. 4.A modular container handling vehicle system according to claim 1,wherein the connecting interface of the wheel base unit comprises ahorizontal top panel featuring multiple connecting elements.
 5. Amodular container handling vehicle system according to claim 1, whereineach of the first and the second container handling module comprises aconnecting interface for connection to the connecting interface of thewheel base unit.
 6. A modular container handling vehicle systemaccording to claim 4, wherein the connecting interface of the first andthe second container handling module comprises connecting elementsarranged at positions corresponding to the multiple connecting elementsof the top panel.
 7. A modular container handling vehicle systemaccording to claim 4, wherein the top panel features a centre openingallowing access to internal components of the wheel base unit.